A hacker successfully breached cryptocurrency mining marketplace NiceHash, resulting in the theft of up to $62 million worth of bitcoins.

The site has been around since 2014 and has been offline, with a message posted that it was "under maintenance".

The kicker comes in the next paragraph, where they write that "importantly, our payment system was compromised and the contents of the NiceHash Bitcoin wallet have been stolen". Users can rent their own mining equipment (cloud computing servers) or they can rent mining equipment (cloud computing servers) from others, splitting profits.

I hope that the bitcoin is able to be recovered or at least that Nicehash is able to do the right think and compensate its users from its own funds. We are working to verify the precise number of BTC taken.

NiceHash head of marketing Andrej P. Škraba told Reuters on Thursday that the hack was "a highly professional attack with sophisticated social engineering" and that about 4,700 bitcoin, worth about US$63.92 million at current prices, were lost.

The company stated that, in addition to an internal investigation, they had contacted the "relevant authorities and law enforcement" and that they are working to "rectify the matter in the coming days".

Site operators advised users to change their passwords when the site returns online.

While the NiceHash operators seem honest with their statement, those words ring hollow for users that lost their accumulated BTC.

The company added that it was "fully committed to restoring the NiceHash service with the highest security measures at the earliest opportunity", but having experienced such a significant blow, how it will manage to return to trading without the ability to provide funds to those using its service is not clear at this point. "We will endeavour to update you at regular intervals".